Manufacture of ferrous alloys and of weatherproof articles therefrom



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JQHN MURDOCH smnnr, DE LONDON ENG-IlZtALhTD, ASSIGNOR TO THE CONTINUOUSv REAC'IIQN COMPANY, LIMITED, OF LONDON, ENGLAND.

MANUFACTURE @F FEBRD'US ALLOYS l lo Drawing.

To all whom it may concern Be it known that 1, Joan MURDOGH Srcrranr, asubject of the King of Great Britain, residing at 155 Ghurch Road, Bat-Cl tersea, London, England, have invented new and useful Improvements inthe Manufacture of Ferrous Alloys and of Weatherroof Articles Therefrom,of which the folowing is a specification.

This invention relates to the manufacture of certain ferrous alloys andto the production from such alloys of manufacturedartiples the use ofwhich involves their expost re to alternate wetting and drying, to todamp and varying atmos heric conditions,

or to like influences whic cause the rusting ]&of articles .made ofordinary iron or stee As is'wellknown, polished hardened artiac cles;such as cutlery, of the kind commonly called stainless are manufacturedfrom iron-chromium alloys containing about 12 to 15 per cent of chromiumand small percentages of carbon, silicon and other constituents. In myexperience such alloys, although serving for the production of articleswhich are sufiiciently untarnishable under the conditions of domesticuse, are of somewhat limited applicability. They cannot be successfullyused for the manufacture of unpolished, weatherproof articles, such asimple ments, fittings, plates, castings, and the like, which have towithstand for long periods exposure to alternate wetting and drying, todamp and varying atmospheric COIldltions, or to like influences.Moreover, it is necessary both to harden by heat-treatment and to imparta polished surface to articles of that composition in order to renderthem reasonably untarnishable under the conditions of use for which theyare intended. So far as I am aware, n article of such alloys hashitherto been made which, when exposed in a clean but unpolishedcondition, (for example, after drilling, machining, rough bufing orgrinding) to the action of rain and sunshine would not become rusted inthe course of a few days.

This invention relates to the manufacture of the iron-chromium alloyshereinafter described and the production from these a1- lo s ofmanufactured articles, hereinafter ca led for brevity weatherproofarticles the use of which involves their exposure to AND or.wnarnnnrnoor .elnrrcnns THERE- rnonr.

Application nlcd June 11, 1928. Serial No. 644,751.

alternate wetting and drying, to damp and varying atmosphericconditions, or to like influences, and which in a polished or unpolishedcondition, and whether. hardened or not, are capable of withstandingsuch exposure for prolonged periods without rustmg. Examples of sucharticles are plates, rails, girders, cast objects, automobile parts,iitensils, implements and tools for out-d'oor use; ships fittings;bathroom fittings; burnished fenders; cooking stoves andthe like whichare liable to have liquid spil-t on them.

It is known that iron and chromium can be alloyed with one another inwidely different, and probably in all, proportions. It is also knownthat the alloys rich in chromium are comparatively resistant to theaction of acids, but are of littlepractical in terest for the productionof manufactured articles owing to their high cost, the difficulty ofWorking them, and their defective -physical and mechanical properties.We

higher the percentage of carbon, the higher the percentage of chromium)can be readily cast or Worked and that articles -manufactured of it arehighly resistant to rusting when used in the rain or otherwise exposedto damp and varying atmospheric influences. l have also found that, theusual minor constituents of commercial steels have little or noprejudicial effect upon the weatherproof properties of articles made ofthe alloy. It is not necessary either to harden or to polish sucharticles in order to render them weatherproof, although they may be sotreated if desired. \Vhen polished they possess the advantageousproperty that if accidentally scratched or roughened they remainweatherproof The invention consists in the manufacture of ferrous alloyscontaining from 12 to 24 per cent of chromium, from 0.4 to 3 per cent ofmolybdenum, from 0.5 to 0.85 per cent of carbon and from 0.1 to 1.3 percent of silicon (the higher the percentage of carbon, the higher thepercentage of chromium), with or without the usual minorconstituents ofcommercial steels, and in the the said alloys. Preferably the percentageof carbon in the alloy does not exceed a certain maximum, which dependsupon the percentages of chromium and molybdenum resent, the rule fordetermining the preferred composition (herein termed the rule of maximumcarbon percentage) being as follows With 0.4 to 0.5% Mo the'maximum'percentage of C corresponding to a given percentage Cr should be asstated in the following table (from which intermediate percentages canbe deduced) Alloy containing 0.40.5% Mo.

(PC/0 (I '1 12 0. l 14 O. 3 16 0. 4 18 O. 55 20 0. 65 22 0. 7 5 24: 0.85

- for example, by melting steel, chromium or ferrochromium andmolybdenum or ferromolybdenum in the requisite proportions together inan electric furnace, care being taken to avoid as far as possible anyinclusion of chromium oxide, which might otherwise injure theweather-resisting properties of the alloy. Weatherproof articles arethen made of the alloy by the following usual methodsl If wroughtarticles'are to be produced, the molten metal is cast into ingots andafterwards hammered, rolled or otherwise worked and treated according toknown methods, care being taken at all stages to avoid workingoxide'into the metal, as the presence of particles of oxide on thesurface tends to set up rusting. It is not necessary, in order to renderthe article rustless, to finish the manufacture by polishing thesurface; a simple cleaning by grind I ing, bufing or the like issuflicient. If the 1,4.eaeae object in view is to produce castings, themolten metal is castin moulds in the usual way and the dark, oxidizedskin may afterwards, if desired, be left on the casting without unduerisk of rusting occurring.

E xample 1.

and then hammering and rolling into sheets,

which are cleaned by bufiing and formed into drums in the usual manner.The alloy can be readily cut and drilled.

Plates made of this alloy, either polished or unpolished and drilledpartly through at various points to ofl'er shallow depressions in whichrainwater might lodge, have been openly exposed during some weeks ofrainy weather and have not rusted.

' Example 2.

' An alloy containing 17 .46 per cent of chromium, 0.47 per cent ofcarbon, 1.2 percent of silicon and 1.1 per centof molybdenum is preparedas in Example 1.

Range-finder parts to be used in an exposed-situation are manufacturedfrom the alloy by casting it into ingots and workin it'by usual methodsinto the desired articles.

What I claim is 1. A ferrous alloy containing from 12.

to 24: per cent of chromium, from 0.4 to 3 per cent of molybdenum, from0.05 to 0.85

per cent of carbon and from 0.1 to 1.3 per cent of silicon.

- 2. Weatherproof articles manufactured from a ferrous alloy containingfrom 12 to 24 per cent of chromium, from 0.4 to 3 per cent ofmolybdenum, from 0.05 to 0.85 per cent of carbon and from 0.1 to 1.3 percent of silicon. I v

lin testimony that I claim the foregomg as my invention 1 have signed myname this v 28th day of May 1923.

JOHN itinianocn SKJELILEY;

